Scaling A Newly Made Cube
What to do

You need to play around with the python console for this stuff.

Here is probably what you want (sets the value directly in the properties panel, absolute method):

bpy.ops.mesh.primitive_cube_add()
bpy.context.scene.objects.active.scale = (-2.2, 0, 0)


You may also want to scale like this (scales object the same way as pressing S in the 3D view, relative method):

bpy.ops.mesh.primitive_cube_add()
bpy.ops.transform.resize(value=(-2.2, 0, 0))


When an object is created, it is selected and set active so my examples will work in a simple case like this without a reference to the object.

Why your script won't work


bpy.ops.mesh.primitive_cube_add doesn't do anything useful (it won't create an object)
bpy.ops.mesh.primitive_cube_add() only returns {'FINISHED'} not a reference to the new object.